X-RAY CRYSTAL-STRUCTURES OF 2 (ETHYLIDYNE)TRICOBALT CLUSTERS - THERMOLYSIS OF CP-ASTERISK-CO(H2C=CH2)2 PRODUCES CP-ASTERISK-3CO3(MU(3)-CCH3)(MU(3)-H), NOT CP-ASTERISK-3CO3(MU(3)-CCH3)2

The structures of the mu3-ethylidyne tricobalt clusters Cp3Co3(mu3-CC H3)2 (2) and Cp3Co3(mu3-CCH3)(mu3-H) (3) were determined by X-ray cry stallography. The 48-electron cluster 2 consists of an equilateral tri angle of cobalt atoms (Co-Co = 2.437(1) angstrom) symmetrically capped on each face by a mu3-CCH3 ligand. Cluster 3 was necessarily disorder ed by the crystallographic site symmetry (3/m) and was therefore refin ed by employing a mirror-disordered model (3a) which assigned half-wei ght to the disordered mu3-CCH3 ligand. The 46-electron cluster 3a cons ists of an equilateral triangle of cobalt atoms (Co-Co = 2.378(1) angs trom) symmetrically capped on a single face by a mu3-CCH3 ligand.